Mark Harmon as Gibbs wearing a navy blue NCIS hat and jacket

Mark Harmon as NCIS Special Agent Leroy Jethro Gibbs.

Photo: Sonja Flemming/CBS

Test your NCIS IQ by filling in the blanks of Gibbs' Rules.

NCIS Special Agent Leroy Jethro Gibbs (Mark Harmon) lives by an extensive list of guidelines, appropriately called "Gibbs' Rules." Rule No. 11? "When the job is done, walk away." And that's exactly what happened at the end of the Oct. 11 episode of NCIS, "Great Wide Open."

After 18 seasons, Harmon ended his impressive run as a series regular—as his onscreen counterpart gave up his badge to stick around in Alaska indefinitely. But fans of the long-running procedural need not fret. In a statement about the series star's departure, NCIS EP/showrunner Steve Binder had this to say regarding Harmon's future: "As longtime fans of the show may have noticed over the years … never count Leroy Jethro Gibbs out."

So, how well do you know Gibbs? Take our quiz and find out!

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